Table 1.
Characteristic Features of Major BRD Pathogens.
Table 2.
Pathogens, doses, and animals.
Table 3.
Scoring system for Clinical Signs.
Fig 1.
Time course of the mean clinical scores for steers infected with viral pathogens and mock infected controls.
Infection with (A) BRSV occurred on day 0 and clinical sign scores are presented for the next seven days. Mean (n = 4) scores were significantly different for both treatment versus day effect and for treatment versus mock infected controls (p<0.005); Bonferroni post hoc test p<0.05. (B) IBR infection occurred on day 0 and mean clinical sign scores are presented for the next six days. Mean (n = 4) scores were highly significantly different from mock infected controls; and treatment versus day effect was significant (Bonferroni test p<0.05). (C) BVDV infection on day 0 was followed until day 15 and mean clinical scores are presented for infected and mock infected controls. The effect of infection (p = 0.0013) and day (p = 0.0071) were significant. Mean clinical sign scores were significantly different for infected and control steers only on day 8 (Bonferroni p<0.058).
Fig 2.
Time course of the mean clinical scores for infected steers infected with bacterial pathogens and mock infected controls.
Infection with (A) Pasteurella multocida on day 0 was followed until day 6. At no time was the difference in mean clinical scores significantly different between infected (n = 4) and mock infected control steers (n = 4). (B) Day 0 infection with Mannheimnia haemolytica was followed for five days. Mean clinical scores were significantly different from day 2 through day five between infected (n = 4) and control steers (p = 0.00135); and the effect of infection and treatment was significant (p = 0.0071), Bonferroni test p<0.05. (C) Infection with Mycoplasma bovis on day 0 was followed through day 15 and the difference in mean clinical scores was significant from day 3 through day 15 (Bonferroni p, 0.05). The effect of infection (p = 0.0054) and day (p = 0.0028) was significant.
Fig 3.
Bacterial isolations from pharyngeal swabs.
To evaluate the presence of the BRDC bacterial pathogens in the posterior pharynx of steers before and after infection, sheathed swabs were taken at intervals and at necropsy. The number of steers from each pathogen infection group (x axis) that had each of the bacterial pathogens isolated from the upper respiratory tract either during infection or at necropsy is shown (y axis).
Fig 4.
The number of virus infected steers with specific pathological lesions-combined pilot and optimized studies
(A-K on x axis) is shown for steers infected with: (A) BRSV, (B) IBR, and (C) BVDV. Lesions are: A) total lung consolidation >1%, B) neutrophilic proliferative necrotizing bronchiolitis/bronchitis, C) supperative bronchopneumonia, D) syncytial formation, E) neutrophilic alveolitis, F) plasmacytic bronchitis/bronchiolitis, G) bacterial culture positive, H) ulcerative rhinitis, I) laryngeal ulceration or erosion, J) tracheal ulceration, K) intranuclear inclusion bodies.
Fig 5.
The number of bacterial infected steers with specific pathological lesions
(A-F)-combined pilot and optimized studies. + on x axis) is shown for steers infected with: (A) Mannheimnia haemolytica, (B) Pasteurella multocida, and (C) Mycoplasma bovis. Lesions are: A) total lung consolidation <1%, B) neutrophilic bronchitis/bronchiolitis, C) subacute necrotizing fibrinocellular lobar pneumonia and pleuritis, D) neutrophilic bronchopneumonia with necrosupperative obliterating bronchiolitis/bronchitis, E) lymphocytic bronchitis/bronchiolitis, F) lymphoid hyperplasia.
Fig 6.
Examples of gross pulmonary pathology from virus infected steers:
(A) BRSV infected lung showing lobar lung consolidation (dark areas), (B) IBR infected lung with consolidation (arrow) and scattered areas of atelectasis and necrosis, (C) IBR infected larynx showing areas of ulceration and erosion (arrow), and (D) BVDV lung showing minimal pathology with scattered small areas of consolidation (arrow).
Fig 7.
Examples of gross pathology from bacterial infected steers:
(A) Mannheimnia haemolytica lung showing consolidation (arrow) and (B) Lung from Mannheimia haemolytica infected steer demonstrating irregular dark red consolidated regions bordered by light grey inflammatory infiltrate with expanded interlobular septa. (C) Pasteurella multocida infected lung with minimal lesions consisting of scattered areas of consolidation (arrows), and (D) Lung from Mycoplasma bovis infected steer demonstrating a focal region (lower left) of consolidation associated with bronchitis with luminal exudate.
Fig 8.
Histopathology of lung from BRSV infected steer.
(A) Bronchiolitis with epithelial necrosis and numerous syncytia (arrows), (B) Immunohistochemistry stain showing positive stain for BRSV in bronchioles (brown color and arrow).
Fig 9.
Histopathology of pharynx from IBR infected steer.
(A) Focal ulcerative pharyngitis with epithelial necrosis (area indicated by length of the arrow), (B) Immunohistochemistry of lesions demonstrating positive cytoplasmic staining for IBR, indicated by arrows and red/brown color.
Fig 10.
Histopathology of the ileum from a BVDV infected steer.
(A) shows section of ileum with depletion of lymphocytes from Peyer’s patches (arrows), and (B) Immunohistochemistry showing positive staining for BVDV in ileum of infected steer (arrow showing brown color).
Fig 11.
Histopathology of the lung from a Mannheimnnia haemoytica infected steer.
Lobar pneumonia with irregular multilobular zones of coagulation necrosis and fibrinocelluar exudation bordered by dense bands of necrotic leukocytes (arrows).
Fig 12.
Histopathology of the lung from Mycoplasma bovis infected steer.
(A) necrosuppuratve bronchiolitis with peribronchiolar mixed leukocytic infiltrate (arrow), (B) Immunohistochemistry of lesion demonstrating positive staining for Mycoplasma bovis in the bronchiolar luminal exudate (brown color and arrow).